1. Field of the Invention
The present invention relates generally to the field of telephony. More specifically, the present invention discloses an interface system for insertion between the telephone handset and base that provides for automatic switching between voice and data communications.
2. Statement of the Problem
The present invention is intended to address two separate, but related problems in communicating both voice and data by telephone. First, it is often desirable to be able to transmit data over a single telephone line interspersed with verbal discussions between the parties. This data can be in the form of visual images relevant to the conversation. For example, a travel agent might wish to show a telephone customer a travel itinerary as they discuss it, or a broker might want to show a customer a visual confirmation of a financial transaction that the customer has just made orally over the telephone. Image data can be transmitted over a telephone line, for example, using conventional facsimile machines or the VoiceView.TM. products marketed by Radish Communications Systems, Inc. of Boulder, Colo. Alternatively, this data can be in the form of one or more data files to be transferred by modem between the parties' computers. A number of telephone systems have been invented in the past to allow transmission of both voice and data over a single telephone line by switching between voice and data modes, including the following:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Davis 5,164,982 Nov. 17, 1992 Emmons et al. 4,932,047 June 5, 1990 Yoshida 4,815,121 Mar. 21, 1989 Artom 4,387,271 June 7, 1983 ______________________________________
Davis discloses a telecommunications display system for accommodating both voice and data over a single telephone line. The receiving party ("subscriber") is provided with a display terminal 14 that is connected to the telephone line 22, 52 between the telephone network 50 and the base of the user's telephone 12 as shown in FIG. 1. The display terminal includes a voice/data selector that can automatically recognize digital data and switches from voice communication to data communication modes. This patent discusses one embodiment of the VoiceView# products marketed by Radish Communications Systems, Inc.
Emmons et al. disclose an example of a conversational video phone. The device communicates both audio signals and freeze-frame video images over a standard telephone line.
Yoshida et al. disclose a telephone communication system that recognizes speech and automatically switches from data to speech transmission.
Artom discloses another example of a telephone system for combining voice and data communications over a single telephone line.
The second problem addressed by the present invention arises from the difficulty of interfacing with the multitude of existing PBX telephone systems that employ proprietary communications protocols between the PBX and its station telephones. Conventional modems, fax machines, and the like are designed to interface only with a standard analog telephone line (i.e., plain old telephone service, or POTS). In facilities having a PBX system, the common solution has been to install additional dedicated analog telephone lines that are not routed through the PBX to service these data devices. This solution adds substantial expense, unnecessary complexity, and wasted telephone line capacity.
The proprietary communications protocols commonly used by PBX systems do not extend farther than the base of the telephone set at each station. In particular, the telephone base and handset are connected by a handset cord that has a pair of speaker lines and a pair of microphone lines for analog communication with the handset speaker and microphone, respectively. Therefore, an alternative approach has been to interface the data device (e.g., a modem or fax) to the handset cord by means of a manually operated switch. The speaker and microphone lines in the handset cord appear to the data device simply as a conventional four-wire analog telephone circuit. This allows the data device to transmit and receive analog-encoded data over the handset cord without having to contend with the communication protocol of the PBX system. A number of prior art patents discuss switching arrangements to accommodate both voice and data transmission by inserting a manual switch into the handset cord, including the following:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Gutzmer 4,907,267 Mar. 6, 1990 Serrano 4,367,374 Jan. 4, 1983 ______________________________________
Gutzmer discloses a manual switch for insertion between a telephone handset and base to accommodate both voice and data transmission. Serrano discloses another example of a manual switch inserted between a telephone handset and base to allow both voice and data transmission. A number of similar manual switches are also on the market.
The shortcoming of a manual switch is that the user must manually operate the switch to change from voice to data transmission. In addition, in order to receive data, the sending party must verbally advise the user that data is about to be transmitted and wait while the user at the receiving end manually changes the switch to data mode. This is relatively slow and cumbersome, particularly if the parties wish to switch back and forth between voice and data communications a number of times during a conversation. It also presents the possibility that data can be inadvertently lost or damaged, and voice communications can be lost or clipped due to mis-timed operation of the manual switch. This possibility is further increased if both parties are manually switching between voice and data modes.
The manual switching arrangement discribed in the Gutzmer patent has been improved upon in two products manufactured by Unlimited Systems Corp., Inc. of San Diego, Calif. These products are described in the "KONEXX Model 112 Operating Instructions" and the "KONEXX Model 108 Operating Instructions." Both KONEXX devices are intended to provide an interface between the telephone base and handset for a data device, such as a fax machine or a modem. The user manually takes the telephone handset off-hook and places a call to a remote station. For example, when used with a fax machine, the user would place a call to the remote fax machine. Similarly, when used with a modem, the user would place a call to the remote modem (e.g., a bulletin board service). When the remote station answers the call, the user must then manually prompt the data device (i.e., the fax machine or modem) to go off-hook and begin communications with the remote station. The KONEXX device detects the increased current through the telephone line connecting the KONEXX device to the data device when the local data device goes off-hook and automatically couples the data device to the telephone base.